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R & S E K 8 9 5 / R & S E K 8 9 6
User Manual
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IF / AF Processor
1.3.9 IF / AF Processor
1.3.9.1 Design
The IF / AF processor consists of a printed cir>
cuit board and a DSP module (A1, DSP = Digi>
tal Signal Processor), a set of screens, two RF
covers, two red extracting levers, the interface
to the carrier board as well as HF interfaces.
The IF / AF processor is connected via the HF in>
terfaces and cables contained in the cable set
to the rear panel, the HF unit and the syn>
thesizer. In addition, the IF / AF processor is
connected via a 5>way connector (X79) and a
signal line to the rear panel.
1.3.9.2 Functioning
(See Figs. 1.12 and 1.13)
The IF / AF processor has a dynamic range of
approx. 90 dB.
The IF2 signal (1.44 MHz) from the HF unit is
fed via a filter and an amplifier to a converter
stage. The latter converts the IF2 signal by
using an auxiliary frequency into the third in>
termediate frequency of 25 kHz. The auxiliary
frequency is obtained from the 5.66>MHz fix
frequency of the synthesizer with the aid of a
4:1 divider. The converter stage is followed by
an analog / digital converter. The digital signal
produced by this converter is evaluated by the
DSP. Synchronization of the A / D converter is
carried out with a frequency of 12.8 MHz. This
frequency is produced from the 40>MHz fix fre>
quency of the synthesizer by two dividers (2:1,
50:1) and a phase>locked loop (PLL).
The DSP has the following functions:
f IF filtering in the following fixed band>
widths (in Hz):
150, 300, 400, 600, 800, 1000, 1500, 1800,
2100, 2400, 2700, 3100, 3600, 4000, 4800,
6000, 8000
or
128 quasicontinuously adjustable filter
bandwidth
f IF control for the following control types
and times: AGC, MGC, AGC+MGC,
AGC+DGC, 25 ms, 150 ms, 500 ms, 1 s, 3 s
f Generation of the AGC>HF voltage for the
control amplifier in the HF unit
f Evaluation of the MGC voltage adjusted by
means of the HF control (control unit 2
∫LOCAL∫ (R&S EK 895), = option 'Control
Unit R&S GB 890' or control unit (R&S
EK!896))
f Generation of the IF signal with a fre>
quency variable between 300 Hz and 40
kHz or optionally with a fix frequency of
455 kHz (IF Converter R&S UX 895). Here
the stepwidth is 10 Hz. The bandwidth of
the IF signal is either the set bandwidth
(150!Hz to 8 kHz) or the maximum band>
width of approx. 10 kHz.
f Demodulation for the following modula>
tion types:
AM, FM, USB, LSB, ISB, CW, FSK, AFSK, FAX,
F7B
The FSK, AFSK and F7B demodulators can
be adapted to the different baud rates and
deviation frequencies in order to yield opti>
mum results.
f Filtering by two independent notch filters
in the range of >5 to 5 kHz. Here the step>
width is 10 Hz.
f Syllable squelch
f Suppression of pulse>shaped interences at
the antenna input (= noise blanker).
f Mean>value indication for the modulation
types AM, FM, CW and FAX or minimum /
maximum indication for the modulation
types FSK, AFSK, F7B
In addition the DSP provides the following sig>
nals:
f AF signals
AF2 (balanced) or FM>Video
AFL and I>component of the AF signal
AFOUT or Q>component of the AF signal
The AF2 level is adjustable via the variabel
resistor LINE2 in the range between >10
and +10 dBm.
f FSK bus (TTL or V.28 level and signal)
f Serial data bus (SData, SCLK, SFrame)
In the CM test the oscillator levels of the 200:1,
50:1 and 10:1 dividers, the 20>MHz signal, the
DSP watchdog and the logic circuitry for over>
load protection are continuously monitored.
Once a fault is detected, it will be signalled to
the processor via the IRQCM line.
6164.0717.02_01
> 1.22 >
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